BACKGROUND: Modified fenestrated stent grafts have been used for compassionate treatment of large complex aortic aneurysms in high-risk patients who do not have access to a manufactured device and are not candidates for conventional open surgical repair. Accurate device design and precise implantation are key components of the procedure. A technique of device modification with diameter-reducing wire is described to facilitate catheterization of side branches.METHODS: The modified Cook Zenith stent graft was created using reinforced fenestrations with gold nitinol markers. The stainless steel wire, which secures the top cap into the uncovered stent, was partially withdrawn, retrieved, and redirected externally through-and-through the fabric of the stent graft. Each Z-stent was constrained using the stainless steel wire for support and by two nonlocking prolene loops. The constrained stent graft was 30% narrower than the unconstrained device, which allowed flow between the stent graft and the aortic wall, as well as longitudinal and rotational movement of the stent graft. After successful catheterization of the fenestrations, balloon-expandable stent grafts were advanced over hydrophilic sheaths, and the stainless steel diameter-reducing wire was removed with full expansion of the Z-stents to its unconstrained diameter. The fenestrations were stented with balloon-expandable stent grafts, followed by placement of iliac limbsCONCLUSION: The use of a diameter-reducing wire allows longitudinal and rotational movement to the modified fenestrated stent graft and facilitates side branch catherization in patients in whom there is misalignment between the fenestration and the origin of the target vessel.